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以粉煤灰为原料,采用两步法合成了单一沸石矿物种的NaA型沸石,对合成产物的结构和性能进行了表征.通过静态吸附实验,研究了NaA型沸石对水溶液中Cu(ΙΙ)、Cr(Ⅵ)和Zn(ΙΙ)离子的吸附特性,从动力学角度探讨了吸附机理.结果表明,在所研究的浓度和pH值条件下,NaA型沸石对3种重金属的吸附符合Langmuir等温吸附方程,静态饱和吸附量(Qm)分别为82.30,65.96,47.78mg/g;3种金属离子在水溶液中的存在方式和大小是影响它们吸附行为的主要因素,通过动边界模型推算表明:NaA型沸石对Cu(ΙΙ)和Zn(ΙΙ)离子的吸附过程的速度控制步骤为液膜扩散,对Cr(Ⅵ)离子的吸附过程的速度控制步骤为颗粒扩散,3种金属离子的吸附过程符合伪二级方程. 相似文献
213.
PCDDs/DF and Co-PCB (dioxin) formations were studied with ash from a newly developed gasification and melting process for
municipal solid waste. Ash samples were heated in a laboratory-scale fixed-bed reactor. Emphasis was placed on the effects
of the type and composition of ash, temperatures, gas residence time, and gaseous organic precursors. Investigations using
macroscopic and homologue distribution analyses led to the following conclusion. The ash from the gasification–melting process
had the ability to generate dioxins in flue gas. A possible carbon source is unburned carbon in the ash samples, although
this was very low (less than 0.01%). An experimental result that the level of dioxins generated from preheated fly ash obtained
from a conventional incinerator was much lower than that from nonheated fly ash supported this conclusion. Dioxin concentrations
obviously showed temperature dependence and peaked at 350°C. Dioxins formed in a gasification–melting process ash were readily
desorbed from the surface, probably because of the low carbon content of the ash. There was no experimental evidence that
gaseous organic precursors fed to the reactor generated dioxins. Therefore, an organic precursor was not essential for the
formation of dioxins. A good linear relationship obtained between PCDDs/DFs and gas residence time also supported the assumption.
Received: February 14, 2000 / Accepted: June 30, 2000 相似文献
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Soil pollution in day-care centers and playgrounds in Norway: national action plan for mapping and remediation 总被引:1,自引:1,他引:0
Ottesen RT Alexander J Langedal M Haugland T Høygaard E 《Environmental geochemistry and health》2008,30(6):623-637
Systematic geochemical mapping based on sampling and analysis of surface soils (0–2 cm) has been carried out in several Norwegian
cities. The soils in the oldest parts of the cities are contaminated with metals (especially Pb) and polycyclic aromatic hydrocarbons
(PAH). Due to the fact that children are often in contact with surface soil, it was realized that special focus had to be
directed towards soils in day-care centers and playgrounds. The first mapping and remedy program was initiated in Trondheim
in 1996. Here, the importance of copper–chromium–arsenic (CCA)-pressure-impregnated wood in playing equipment as a pollution
source for soils was documented, and a process was started with the aim to ban this product. Soils from day-care centers in
the inner city of Bergen were polluted to a degree that required remediation in 45% out of 87 centers, mainly due to high
concentrations of Pb and benzo(a)pyrene. In Oslo, 38% of 700 day-care centers needed remediation due to soil pollution by
Pb, BaP, Cd, Hg, Ni and PCB. Removal of CCA-impregnated wood was necessary in more than half of the day-care centers The Norwegian
parliament has decided to investigate all outdoor playing areas in day-care centers, playgrounds and schoolyards in Norway,
starting in 2007 with day-care centers in the ten largest cities and five most important industrial areas. The Norwegian Institute
of Public Health has developed quality criteria for soils in day-care centers and playgrounds for As, Cd, Cr6+, Hg, Ni, Pb, zinc, PAHsum16, benzo(a)pyrene, and PCBsum7. The Geological Survey of Norway has developed guidance for mapping of soil pollution (sampling, chemical analysis and reporting)
in day-care centers. Especially the sampling strategy has been developed in the period 1996–2007, and the preferred sampling
strategy is to collect at least 10 samples of surface soil (0–2 cm) from (1) “original soil” on the site, (2) artificial man-made
“hills”, and (3) soils used for growing vegetables. A total number of 2,000 day-care-centres are to be investigated, and necessary
remediation should be completed before the end of 2010. 相似文献
217.
垃圾焚烧飞灰熔融渣特性分析 总被引:3,自引:3,他引:0
研究了熔融固化产物--熔融渣的特性.结果表明:熔融渣的主要成分为CaO,Al2O3和SiO2,其含量占总质量的99%左右,而SO3,K2O,Na2O和Cl在熔融渣中的含量明显降低,其质量分数分别从原始飞灰中的10.74%,8 58%,3.81%和20.59%降低到0.17%,0.04%,0.23%和0.11%;熔融渣中碱性氧化物和酸性氧化物的含量基本相同,碱度接近于1.0;重金属Cr和Zn的固定率较高,分别为94.2%和81 7%,而Cu,Pb和Cd的固定率较低,分别为31.4%,14.5%和24.6%;采用美国TCLP方法测试的熔融渣中重金属浸出量均低于国家危险废物浸出毒性鉴别标准限值. 相似文献
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Libby, Montana is the only PM2.5 nonattainment area in the western United States with the exceptions of parts of southern California. During January through
March 2005, a particulate matter (PM) sampling program was conducted within Libby’s elementary and middle schools to establish
baseline indoor PM concentrations before a wood stove change-out program is implemented over the next several years. As part
of this program, indoor concentrations of PM mass, organic carbon (OC), and elemental carbon (EC) in five different size fractions
(>2.5, 1.0–2.5, 0.5–1.0, 0.25–0.5, and <0.25 μm) were measured. Total measured PM mass concentrations were much higher inside
the elementary school, with particle size fraction (>2.5, 0.5–1.0, 0.25–0.5, and <0.25 μm) concentrations between 2 and 5
times higher when compared to the middle school. The 1.0–2.5 μm fraction had the largest difference between the two sites,
with elementary school concentrations nearly 10 times higher than the middle school values. The carbon component for the schools’
indoor PM was found to be predominantly composed of OC. Measured total OC and EC concentrations, as well as concentrations
within individual size fractions, were an average of two to five times higher at the elementary school when compared to the
middle school. For the ultrafine fraction (<0.25), EC concentrations were similar between each of the schools. Despite the
differences in concentrations between the schools at the various fraction levels, the OC/EC ratio was determined to be similar. 相似文献